Because energy is used to heat water, it is believed that to be green, carpets should be cleaned with cold water — but not all experts agree.

According to the Institute of Inspection, Cleaning and Restoration Certification (IICRC) the four fundamental factors involved in effective cleaning are heat, time, agitation and chemical action. Additional studies indicate that heat speeds up chemical activity by a factor of two for every 18 degrees of temperatures above 118 degrees Fahrenheit.

According to Dr. Michael Berry, a research professor at the University of North Carolina at Chapel Hill, heated water/solution also makes soils more soluble, helping to dissolve and remove them from the carpet. It also allows workers to use less chemical to dissolve a given amount of substance.

Whenever less chemical is used in the cleaning process, it is viewed as greener because this helps reduce cleaning's impact on the environment. Also, when carpets are more effectively cleaned, there is less potential for resoiling.